Continuous trinitrotoluene manufacture



April 30, 1963 E. SAMUELSEN 3,087,973

CONTINUOUS TRINITROTOLUENE MANUFACTURE Original Filed Feb. 7, 1956 2 Sheets-Sheet 1 FIGJ z I J gamma.

ATTORNEY April 1963 E. SAMUELSEN 3, 87,973

CONTINUOUS TRINITROTOLUENE MANUFACTURE Original Filed Feb. 7, 1956 2 Sheets-Sheet 2 FIG.Z

A TTORNE Y.

United dtatcs atent 3,087,073 CONTENUGUS TRHNETROTOLUENE MANUFAQTURE Eirik Samuelsen, Gullaug, Norway, assignor to Aktiebolaget Chematur, Stockholm, Sweden, a corporation of Sweden, and Norslr Spraengstofindustrie A/S, @510,

Norway, a corporation of Norway Griginal application Feb. 7, 1956, Ser. No. 564,073, new Patent No. 3,034,867, dated May 15, 1962. Divided and this application Sept. 14, 1961, Ser. No. 142,99

Claims priority, application Sweden Mar. 23, 1955' 2 Claims. (Cl. 260-645) This application is a division of my copending application Serial No. 564,073 filed February 7, 1956, which matured into U.S. Patent No. 3,034,867, granted May 15, 1962.

This invention relates to the nitration of toluene and nitrotoluenes, and particularly to a method for the manufacture of trinitrotoluene by continuous operation.

It has heretofore been proposed to manufacture trinitrotoluene by continuous operation in a series of nitrators and separators, as represented, for example, by the United States patent to Holley and Mott No. 1,297,- 170, to Hoek No. 2,475,095 and to Norell No. 2,594,675.

In all of these older proposals the mixture from a reaction vessel or nitrator is continuously fed to a separator in which nitrobody is separated from acid; the former being fed to the next nitrator in the series and the latter to a preceding nitrator and so on. In such systems the hold-up time in the nitrator will be of the same order for the toluene or nitrobody as for the nitrating acid.

It has now been found that when the nitrating acid is given a longer hold-up time in comparison with the toluene or nitrobody in the nitrators several advantages over older processes are obtained. The nitration will be more complete in each step and a higher yield of trinitrotoluene will be obtained. Such a difference in hold-up time can be arrived at simply by returning part of the separated acid to the nitrator.

The object of the present invention is, generally stated, to provide a process for continuous trinitrotoluene manufacture in a series of nitrators and separators in which the hold-up times of the reaction phases may be chosen at will.

Another object of this invention is the provision of such a process by which the volume of the separator can be made smaller than usual, thus reducing the quantities of explosives in operation, i.e., obtaining greater safety in operation.

Other objects will become apparent to those skilled in the art when the following description is read in connec tion with the accompanying drawings.

In accordance with the present invention, generally stated, partially separated emulsions are fed back from the separators to the nitrators, i.e., part of the emulsions introduced into the separators are brought back to the nitrators after that part of the disperse-phase or nitrobody has separated. It is desirable to feed back a quantity amounting at least to the half part of the total quantity of the separated products, i.e., nitrobody and acid, which are leaving the separator. Normally the return current will be larger, say 5-15 or more times, the summary of the separated products leaving the separator. With a large return current of partly separated emulsion, it is possible to bring down the quantities of unreacted toluene or nitrobody in the reaction products leaving the seperators to negligible amounts. With a large return current only the larger drops or the more easily separated particles in the emulsion separate and go into the homogenous phase of outgoing nitrobody. The smaller drops or particles in the emulsion, which necessarily must ice have a longer time to separate, are returned to the nitrator to enter into a new mixing operation. The separator can thus be made smaller and proportioned after the times necessary to separate the desired part of the emulsion.

The apparatus for carrying out the method of the invention consists of a system of nitrator-separators, equipped with mixing devices, cooling devices, inlets and outlets for acids, nitrobody, etc., as in other continuous toluene nitrating systems, and with means by which partly separated emulsion can be fed back to the nitrator. It is preferable to hold the level of the nitrobody in the separator above the level in the attached nitrator, to permit the partly separated emulsion to flow to the nitrator by gravity. The transport of emulsion from the nitrator to the separator can be performed with the help of a pump or the like. It is also possible to design the nitrator in such a way that a pumping efiect from the mixing device is obtained. The suction or the pumping effect from a mixing propeller or turbine can thus be used. The nitrator can also be made in the form of a U-vessel with propeller or turbine in one leg. The liquid in the other leg will thus give a higher level to be used for transport of emulsion to the separator.

Referring now to the drawings for an illustrative embodiment of the invention.

FIGURE 1 shows a nitrator 1 with attached separator 2. The nitrator l is equipped with mixing propeller 3, driven by an electrical motor 4, cooling coils 5, inlets 6 and 7 for toluene or nitrobody respectively nitrating acid. The outlet 8 of the nitrator is connected to the inlet 9 of the separator. Through inlet 10 supplementary acid can be introduced. In the separator there is a lattice, sieve or network 11 to distribute the incoming emulsion. There is also a pipe 12 to withdraw partly separated emulsion to the pump 13 and back to the nitrator 1 through pipe 14 and inlet 15. The amount of partly separated emulsion can be regulated by a valve 16. Separated nitrobody is continuously overflowing at the liquid level of the separator through outlet 17 and separated acid through an outlet 18 from the bottom of the separator. The nitrator as Well as the separator can be modified in many ways. Instead of using a nitrator of ordinary shape as illustrated in FIG. 1, it can for instance be given the shape of a U-pipe as will be described in the following example. The separator can have a conical inlet to get a good distribution of the emulsion without net work and the like. The outlet 12 for partly separated emulsion can have an adjustable prolongation for instance in the shape of a telescopic tube to make it possible to regulate the outlet in vertical as well as horizontal directions. The outlet can also be arranged in one or more of the sides of the separator. It is possible to give the separator vessel the form of a parallelepiped or a lying cylinder with more or less conical ends or of a standing cylinder with tangential inlet for the emulsion.

In FIGURE 2 is shown a combination of two apparatus units, each consisting of nitrator and separator. In a complete apparatus for the manufacture of trinitrotoluene out of toluene at least three apparatus units are needed, one unit for each step of nitration. Normally 5-8- or more units are used as the reactions then are easier to control and higher output is obtained. The principle of a complete series of units will however be easily understood already from a combination of two apparatus units.

The nitrators 1c, dd are in this case formed as U-tu-bes with propeller or turbine 30, 3d in one leg 1%, 19d communicating with the other leg 20c, 20d through bot-tom pipe 21c, 21d. At the upper part of the legs there is an overflow pipe 22c, 22d. With the propeller 3c, 3d in function the liquid will rise in the leg 20c, 200. thus creating sufficient liquid level in the separators 2c, 2d to transport partly separated emulsion back to the nitrators without an extra pumping device.

Toluene or separated nitrobody from a preceding unit in the apparatus series is Continuously introduced in the nitrat-or 1c through inlet 60 and is reacted With separated acid coming from separator 2d through 23rd and introduced through inlet 70. Extra acid (supplementary acid) may be added through inlet c, 10d. Part of the circulating reaction mixture is removed through outlets Sc and conducted to the separator through inlet 90. The reaction mixture partly separates in the separator; the separated n-itrobody being led to the next nitrator 111 through overflow-outlet 17c and inlet 6d of the said apparatus. The separated acid is led through outlet 180 through overflowpipe- 2-30 to the preceding nitrator, or in the case of nitrator 10 being the first one in the units series, to a spent acid tank or to a denitnator. Partly separated emulsion, the quantity being regulated by valve 160, flows back to the nitrator 10 through pipe 12c and 140 respectively inlet 150. V v

In the nitrator 1d and separator 2d the operation principle is the same. In the case that this unit is the last in the unit series, trinitrotoluene is withdrawn from the separator 2d through outlet 17d and fresh nitnating acid, or the components of nitrating acid, introduced into the nitrator through inlets 7d and 10d. Separated acid is removed from separator 2d through overflow-outlet 18d and conducted through pipe line 23d to the nitrator 10.

In a series of units it will be found that feedback of partly separated emulsion has special advantages over feedback of separated components. The Whole system Will be easier to control as the change of the conditions in one unit will not influence the other units. This is easily understood from the fact that the streams of separated products overflowing from the outlets of the separator are of the same size even if the proportions of nitrobody and acid, respectively, the hold-up time of the phases are changed in the nitrators.

The novel apparatus herein disclosed for carrying out the method of the invention forms the claimed subject matter of my aforesaid copending application Serial No. 564,073.

What is claimed:

1. A continuous method of nitration of toluene and nitrotoluenes in a series of zones each consisting of a nitration step (and a separation step, nitrobody being fed in countercurrent to nitrating acid through the system, characterized by return of partly separated emulsion of nitrobody and acid from the separation step to the nitration step in at least one zone of the series.

2. A continuous method of nitration of toluene and nitrotoluene to trinitrotoluene in a series of zones each consisting of a nitration step and a separation step, nitrobody vbeing fed in countercurrent to nitrating acid through the system, characterized by return of partly separated emulsion of nitrobody and acid from the separation step to the nitration step in at least one zone of the series, the returned quantity of partly separated emulsion amounting to at least half of the total quantities of separated nitrobody and acid from the separation step.

No references cited. 

1. A CONTINUOUS METHOF OF NITRATION OF TOLUENE AND NITROTOLUENES IN A SERIES OF ZONES EACH CONSISTING OF A NITRATION STEP AND A SEPARATION STEP, NITROBODY BEING FED IN COUNTERCURRENT TO NITRATING ACID THROUGH THE SYSTEM CHARACTERIZED BY RETURN OF PARTLY SEPARATED STEP TO THE NITRANITROBODY AND ACID FROM THE SEPARATION STEP TO THE NITRATION STEP IN AT LEAST ONE ZONE OF THE SERIES. 